Electric coolant pump control strategy for hybrid electric vehicles

Abstract

This invention relates to a hybrid electric vehicle component coolant control system and method. The coolant system has an electric pump to move coolant through a closed system including engine and motor components. Such components to be cooled can include any electric motors, power electronics, engine, and transmission. The preferred embodiment controls coolant flow to the vehicle engine and motor in a single closed loop. Vehicle components have temperature sensors that send temperature signals to an electric coolant pump duty cycle control strategy. The control strategy makes a determination of a duty cycle of the electric coolant pump as a function of the temperatures of vehicle components and orders the duty cycle of the electric pump. In the preferred configuration, engine temperature sensors can acquire either engine coolant temperature or engine cylinder head temperature. The preferred configuration includes a heater core in the coolant flow path connected between vehicle components and the electric coolant pump return, whereby passenger heating requests are facilitated. Several coolant flow paths among the vehicle components are possible including a parallel and series configuration. The control system can also use a rolling average filter routine connected between the temperature sensor for the motor and the control strategy to determine the average temperature of the motor.

We claim:  
     
       1. A system for controlling coolant flow to cool an electric traction motor and an internal combustion engine of a hybrid electric vehicle (HEV), comprising: 
       an electric coolant pump with an output and a return;  
       a closed coolant flow path connecting to the electric coolant pump output, flowing through the electric traction motor and the internal combustion engine of the HEV to be cooled, and ending at an electric coolant pump return;  
       the electric traction motor and the internal combustion engine having temperature sensors that send temperature signals to an electric coolant pump duty cycle controller; and  
       the controller establishing a duty cycle of the electric coolant pump as a function of temperatures of the electric traction motor and internal combustion engine, wherein at least one of the temperature sensors associated with the electric traction motor generates a signal that is filtered to provide a signal that is adjusted to minimize the effect of rapid excursions in temperature signals.  
     
     
       2. The system for controlling coolant flow to cool components of an HEV of  claim 1  wherein the motor temperature is acquired by sending coolant temperature leaving the motor. 
     
     
       3. The system for controlling coolant flow to cool components of an HEV of  claim 1  wherein a motor temperature is acquired by sensing motor winding temperature. 
     
     
       4. The system for controlling coolant flow to cool components of a hybrid electric vehicle of  claim 1 , wherein an engine temperature is acquired by sensing engine coolant temperature leaving a cylinder head. 
     
     
       5. The system for controlling coolant flow to cool components of a hybrid electric vehicle of  claim 1  wherein the engine temperature is acquired by sensing the engine cylinder head temperature. 
     
     
       6. The system for controlling coolant flow to cool components of a hybrid electric vehicle of  claim 1  wherein the coolant flow path is in a parallel configuration. 
     
     
       7. The system for controlling coolant flow to cool components of a hybrid electric vehicle of  claim 1  wherein the coolant flow path is in a series configuration. 
     
     
       8. The system for controlling coolant flow to cool components of a hybrid electric vehicle of  claim 1  wherein the coolant flow path further flows through a heater core connected between the hybrid electric vehicle components and the electric coolant pump return, whereby passenger heating requests are facilitated. 
     
     
       9. The system for controlling coolant flow to cool components of an HEV of  claim 1  further comprising a rolling average filter routine connected between the temperature sensor for the motor and the control strategy, whereby the average temperature of the motor is acquired. 
     
     
       10. A method for controlling coolant flow to cool an electric traction motor and an internal combustion engine of a hybrid electric vehicle (HEV), comprising the steps of: 
       pumping coolant with an electric coolant pump having an output and a return;  
       flowing the coolant through a closed flow path to the electric coolant pump output, the electric traction motor, the internal combustion engine of the HEV to be cooled, and then returning at an electric coolant pump return;  
       sensing the electric traction motor temperature and the internal combustion engine temperature;  
       signaling the electric traction motor temperature and the internal combustion engine temperature to an electric coolant pump duty cycle controller; and  
       determining a duty cycle of the electric coolant pump as a function of the temperature of the electric traction motor and the internal combustion engine, wherein a rolling average of at least one temperature signal from the electric traction motor is used in determining the duty cycle of the electric coolant pump.  
     
     
       11. The method for controlling coolant flow to cool components of an HEV of  claim 10 , wherein sensing motor temperature is acquired by sensing coolant temperature leaving the motor. 
     
     
       12. The method for controlling coolant flow to cool components of an HEV of  claim 10  wherein sensing motor temperature is acquired by sensing motor winding temperature. 
     
     
       13. The method for controlling coolant flow to cool components of an HEV of  claim 10 , wherein sensing engine temperature is acquired by sensing engine coolant temperature leaving the cylinder head. 
     
     
       14. The method for controlling coolant flow to cool components of an HEV of  claim 10  wherein sensing engine temperature is acquired by sensing engine cylinder head temperature. 
     
     
       15. The method for controlling coolant flow to cool components of an HEV of  claim 10  wherein flowing the coolant through a closed flow path is a parallel configuration. 
     
     
       16. The method for controlling coolant flow to cool components of an HEV of  claim 10  wherein flowing the coolant through a closed flow path is a series configuration. 
     
     
       17. The method for controlling coolant flow to cool components of an HEV of  claim 10  further comprising the step of flowing coolant through a heater core connected between the HEV components and the electric coolant pump return, whereby passenger heating requests are facilitated. 
     
     
       18. The method for controlling coolant flow to cool components of an HEV of  claim 10  further comprising the step of determining a rolling average filter between the temperature sensing step for the motor and the control strategy, whereby the average temperature of the motor is acquired.